Which part of the aircraft receives signals from the DME ground station?

The interrogator is the correct choice because it is the component of the aircraft that actively sends out signals to the Distance Measuring Equipment (DME) ground station. When the interrogator transmits a signal, the DME ground station responds with a signal that allows the aircraft to determine its distance from the ground station. This is a crucial function for navigation, as it provides pilots with information to help maintain situational awareness and accurately determine their position relative to the DME station.

In aviation, the transponder is used for secondary surveillance radar and is not involved in the DME function. The receiver is typically responsible for capturing the signals but does not directly interact with the ground station like the interrogator does. The autopilot is an entirely separate system that assists with controlling the aircraft's flight path and does not engage with DME operations. Hence, the interrogator is specifically designed to handle the interaction necessary for DME distance measurements.